Detailed sedimentary N isotope records from Cariaco Basin for terminations I and V: Local and global implications

• Published in: Global Biogeochemical Cycles
• Main Authors: Meckler, A. Nele, Haug, Gerald H., Sigman, Daniel M., Plessen, Birgit, Peterson, Larry C., Thierstein, Hans R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2007
• Subjects: Cariaco Basin; N fixation; deglaciation; North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00233/34457/32869.pdf; https://doi.org/10.1029/2006GB002893; https://archimer.ifremer.fr/doc/00233/34457/

For the last deglaciation and Termination V ( the initiation of MIS 11 at around 430 ka) we report high-resolution sedimentary nitrogen isotope (delta(15)N)records from Cariaco Basin in the Caribbean Sea. During both terminations the previously reported interglacial decrease in delta(15)N clearly lags local changes such as water column anoxia as well as global increases in denitrification by several thousand years. On top of the glacial-interglacial change, several delta(15)N peaks were observed during the last deglaciation. The deglacial signal in Cariaco Basin can be best explained as a combination of (1) local variations in suboxia and water column denitrification as the reason for the millennial-scale peaks, (2) a deglacial maximum in mean ocean nitrate delta(15)N, and (3) increasing N(2) fixation in response to globally increased denitrification causing the overall deglacial delta(15)N decrease. In the Holocene, much of the decrease in delta(15)N occurred between 6 and 3 ka, coinciding with an expected precession-modulated increase in African dust transport to the tropical North Atlantic and the Caribbean. This begs the hypothesis that N(2) fixation in this region increased in response to interglacial maxima in denitrification elsewhere but that this response strengthened with increased mid-Holocene iron input. It remains to be seen whether the data for MIS 11 support this interpretation.